US20240391724A1

US20240391724A1 - Sheet stacking apparatus and image forming system

Info

Publication number: US20240391724A1
Application number: US18/664,620
Authority: US
Inventors: Toshiya Iseno; Tomoki Nakano
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 2023-05-23
Filing date: 2024-05-15
Publication date: 2024-11-28
Also published as: JP2024168284A

Abstract

A sheet stacking apparatus includes a conveyance unit configured to convey a sheet, a stacking unit on which the sheet conveyed by the conveyance unit is stacked, the stacking unit being configured to be lowered as an amount of the sheets stacked on the stacking unit increases, an abutment portion on which a leading edge of the sheet conveyed by the conveyance unit abuts, an urging unit configured to urge a leading edge portion, of the sheet, abutting on the abutment portion toward the stacking unit, and a control unit configured to adjust an urging force of the urging unit according to sheet information of the sheet conveyed toward the abutment portion.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a sheet stacking apparatus that stacks sheets, and an image forming system.

Description of the Related Art

For example, an image forming apparatus, an image forming system including the image forming apparatus, or the like includes a sheet stacking apparatus that stacks a plurality of sheets on which an image is formed on a stacking unit such as a tray. In such a sheet stacking apparatus, when a plurality of sheets are stacked on the stacking unit, leading edges of the sheets are abutted on an abutment portion to align the sheets. However, for example, when a leading edge of a sheet rises due to curling or the like, there is a possibility that the leading edge of the sheet does not follow the abutment portion and the alignment becomes poor. For this reason, there has been proposed a sheet stacking apparatus that improves alignment of stacked sheets by urging leading edge portions of sheets toward a tray (see JP 2006-256729 A). In JP 2006-256729 A, a weight plate is swingably supported by an arm member, so that a uniform pressing force (urging force) is applied to the leading edge portions of the sheets by the weight plate regardless of a stacking amount of the sheets stacked on the tray.
Meanwhile, in recent years, diversification of sheets on which images are formed has been desired, and in a sheet stacking apparatus that performs alignment by urging leading edge portions of sheets toward a tray as described above, it is also required to stack sheets having greatly different thicknesses (stiffness) on the tray. Then, for example, in a case where sheets having a large thickness (high stiffness) are stacked on the tray and aligned, unless leading edge portions of the sheets are urged with a large urging force, the leading edge portions of the sheets float and the alignment becomes poor, which is problematic. However, when the leading edge portions of the sheets are restrained by a large urging force, for example, in a case where sheets having a small thickness (low stiffness) are stacked on the tray to be aligned, buckling of the sheet or the like may occur. For this reason, for example, in the case of sheets having a small thickness (low stiffness), leading edges of the sheets cannot reach an abutment portion, and the alignment of the sheets becomes poor.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a sheet stacking apparatus includes a conveyance unit configured to convey a sheet, a stacking unit on which the sheet conveyed by the conveyance unit is stacked, the stacking unit being configured to be lowered as an amount of the sheets stacked on the stacking unit increases, an abutment portion on which a leading edge of the sheet conveyed by the conveyance unit abuts, an urging unit configured to urge a leading edge portion, of the sheet, abutting on the abutment portion toward the stacking unit, and a control unit configured to adjust an urging force of the urging unit according to sheet information of the sheet conveyed toward the abutment portion.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view illustrating an image forming system according to a first embodiment.

FIG. 2 is a block diagram illustrating a control system of the image forming system according to the first embodiment.

FIG. 3 is a schematic view illustrating a stacker according to the first embodiment.

FIG. 4A is an enlarged view of a part of the stacker in a state where a draw-in belt according to the first embodiment is lowered.

FIG. 4B is an enlarged view of a part of the stacker in a state where the draw-in belt according to the first embodiment is lifted.

FIG. 5A is an enlarged view of a part of the stacker in a state where an urging lever according to the first embodiment is lowered.

FIG. 5B is an enlarged view of a part of the stacker in a state where the urging lever according to the first embodiment is lifted.

FIG. 6 is a flowchart illustrating control of the image forming system according to the first embodiment.

FIG. 7A is an enlarged view of a part of a stacker in a state where a stacking tray according to a second embodiment is lifted.

FIG. 7B is an enlarged view of a part of the stacker in a state where the stacking tray according to the second embodiment is lowered.

FIG. 7C is an enlarged view of a part of the stacker in a state where sheets according to the second embodiment are stacked on the stacking tray and a sheet holding plate is lifted.

FIG. 7D is an enlarged view of a part of the stacker in a state where the stacking tray is lowered after the sheets according to the second embodiment are stacked on the stacking tray.

FIG. 8A is an enlarged view of a part of the stacker in a state where an upper surface position sensor according to the second embodiment does not detect a position detection lever pressed against an upper surface of a sheet bundle.

FIG. 8B is an enlarged view of a part of the stacker in a state where the upper surface position sensor according to the second embodiment detects the position detection lever pressed against the upper surface of the sheet bundle.

FIG. 9 is a flowchart illustrating control of an image forming system according to the second embodiment.

DESCRIPTION OF THE EMBODIMENTS

First Embodiment

Hereinafter, a first embodiment according to the present disclosure will be described with reference to the drawings.

Configuration of Image Forming System

FIG. 1 is a schematic view of an image forming system 900 according to the first embodiment. The image forming system 900 includes an image forming apparatus 901 (printer unit) that forms an image on a sheet P, and a stacker 100 serving as a sheet stacking apparatus that receives and stacks the sheets P on which an image is formed from the image forming apparatus 901. As the sheet P serving as a recording material (recording medium), various sheet materials having different sizes and materials, such as paper such as plain paper or thick paper, a sheet material subjected to surface treatment such as coated paper, a sheet material having a special shape such as an envelope or index paper, a plastic film, and cloth, can be used.
The image forming system 900 can include an apparatus other than the image forming apparatus 901 and the stacker 100. Examples of such an apparatus include a sheet feeding apparatus (option feeder) that supplies the sheet P to the image forming apparatus 901 and a sheet processing apparatus (finisher) that performs processing such as binding processing on the sheets P.

Configuration of Image Forming Apparatus

The image forming apparatus 901 includes an image forming unit 902, a fixing device 912, a duplex conveyance unit 953, an image reading device 951, and a control unit 960. The image forming unit 902 includes a photosensitive drum 906 serving as an image bearing member, a charger 907, an exposure device 908, a developing device 909, a transfer device 905, and a cleaning device 913. The fixing device 912 is of a heat fixing type including a heating roller, a pressure roller, and a heat source such as a halogen lamp for heating the heating roller.
The image reading device 951 includes a scanner unit 955 and an image sensor 954. A platen glass 952 on which a document is placed is provided on an upper surface of the image forming apparatus 901. Further, a document feeding apparatus 950 that automatically feeds a document is provided above the image forming apparatus 901.
The image forming apparatus 901 includes cassettes 902 a to 902 d serving as sheet housing units, feed rollers 903 a to 903 d serving as feeding units, and a registration roller 910. Further, the image forming apparatus 901 includes a plurality of conveyance roller pairs 904 arranged along a sheet conveyance path, and a discharge roller pair 914 serving as a discharge unit. Further, the sheet feeding apparatus connected to the image forming apparatus 901 includes a cassette 902 e and a feed roller 903 e that feeds the sheet P toward the image forming apparatus 901.

Operation of Image Forming Apparatus

An image forming operation of the image forming apparatus 901 will be described. When an image forming signal is output from the control unit 960, first, a document is fed by the document feeding apparatus 950. The image reading device 951 optically scans a document being conveyed by the scanner unit 955, and converts an optical image into image data (digital data) by the image sensor 954. The image reading device 951 can read image data from a still document placed on the platen glass 952 by moving the scanner unit 955. The image data read by the image reading device 951 is sent to the exposure device 908.
In the image forming unit 902, the photosensitive drum 906 is rotationally driven, and the charger 907 uniformly charges the surface of the photosensitive drum 906. The exposure device 908 irradiates the photosensitive drum 906 with light based on the image data to perform exposure, and forms an electrostatic latent image on the surface of the photosensitive drum 906. The developing device 909 supplies toner serving as a developer to the photosensitive drum 906 to develop the electrostatic latent image into a toner image. The toner image is borne on the photosensitive drum 906 and conveyed toward a transfer portion where the photosensitive drum 906 and the transfer device 905 face each other.
On the other hand, a sheet conveyance operation is performed in parallel with formation of the toner image in the image forming unit 902. When a feed signal is output from the control unit 960, the sheets Pare fed one by one from one of the cassettes 902 a to 902 e by the feed rollers 903 a to 903 e. The fed sheet P is subjected to skew correction by the registration roller 910, and then conveyed to the transfer portion at a timing synchronized with the toner image formed by the image forming unit 902. Then, the toner image is transferred from the photosensitive drum 906 to the sheet P in the transfer portion by an electric field bias formed by the transfer device 905. The cleaning device 913 removes, from the surface of the photosensitive drum 906, deposits such as transfer residual toner that has not been transferred from the photosensitive drum 906 to the sheet P in preparation for the next image formation. The sheet P having passed through the transfer portion is conveyed to the fixing device 912 by a conveyor belt 911. The fixing device 912 fixes the toner image on the sheet P by heating and pressurizing the toner image on the sheet P while nipping and conveying the sheet P.
The sheet P having passed through the fixing device 912 is guided to the discharge roller pair 914 or the duplex conveyance unit 953 by a switching member 915. In the case of single-sided image formation (single-sided printing) in which an image is formed on one side of the sheet P, the sheet P is guided by the discharge roller pair 914 and discharged from the image forming apparatus 901 by the discharge roller pair 914. In the case of duplex image formation (duplex printing) in which images are formed on both sides of the sheet P, the sheet Pin which an image is formed on a first side is guided to the duplex conveyance unit 953. The duplex conveyance unit 953 conveys the sheet P to the registration roller 910 again in a state where the sheet P is reversely conveyed (switched back) and the first side and a second side are reversed. Then, after an image is formed on the second side of the sheet P by passing through the transfer portion and the fixing device 912, the sheet P is discharged from the image forming apparatus 901 by the discharge roller pair 914.
Although the image forming operation based on image data read from a document by the image reading device 951 has been described here, the image forming system 900 can also perform the image forming operation based on, for example, image data received from an external computer. The image forming unit 902, which is a direct transfer type electrophotographic unit described above, is an example of an image forming unit that forms an image on the sheet P. The image forming unit may be, for example, an intermediate transfer type electrophotographic unit that transfers a toner image from an image bearing member to a sheet via an intermediate transfer body, an inkjet type printing unit, or an offset type printing unit.

Control System of Image Forming System

FIG. 2 is a block diagram illustrating a control system of the image forming system 900. The control unit 960 (see FIG. 1 ) of the image forming apparatus 901 includes a central processing unit (CPU) circuit unit 206, an external interface (I/F) 201, a document feeding control unit 202, an operation unit 209, an image reader control unit 203, an image signal control unit 204, and a printer control unit 205. The CPU circuit unit 206 includes a CPU, a read only memory (ROM) 207, and a random access memory (RAM) 208. The CPU reads and executes a control program stored in the ROM 207 to comprehensively control the document feeding control unit 202, the operation unit 209, the image reader control unit 203, the image signal control unit 204, the printer control unit 205, and a stacker control unit 210.
The RAM 208 temporarily holds control data and is used as a work area for arithmetic processing associated with control. The document feeding control unit 202 performs drive control of the document feeding apparatus 950 based on an instruction from the CPU circuit unit 206. The image reader control unit 203 performs drive control of the scanner unit 955 and the image sensor 954 of the image reading device 951, and transfers an analog image signal output from the image sensor 954 to the image signal control unit 204. The image signal control unit 204 performs each processing after converting the analog image signal from the image sensor 954 into a digital image signal, converts the digital image signal into a video signal, and outputs the video signal to the printer control unit 205.
The external I/F 201 is an interface between the image forming system 900 and an external computer 200. The external I/F 201 develops image data received from the computer 200 into a bitmap image, and outputs the bitmap image as a digital image signal to the image signal control unit 204. The image signal control unit 204 performs various types of processing on a digital image signal received from the external I/F 201, converts the digital image signal into a video signal, and outputs the video signal to the printer control unit 205. A processing operation performed by the image signal control unit 204 is controlled by the CPU circuit unit 206.
The printer control unit 205 drives the exposure device 908 via an exposure control unit based on an input video signal. The operation unit 209 includes an input device (a touch panel, a button, or the like) that receives an operation of changing settings (job settings) of various functions at the time of image formation, and a display device (a liquid crystal panel) that displays information indicating current job settings for a user or the like. The operation unit 209 displays information regarding the display device based on an instruction from the CPU circuit unit 206, and outputs a signal corresponding to a user operation performed on the input device to the CPU circuit unit 206. The user can set attribute information (hereinafter, referred to as sheet information) of the sheet P used for the image forming operation through an operation of the operation unit 209. The sheet information is, for example, information regarding the size of the sheet P, the grammage of the sheet P, the material (coated paper, plain paper, recycled paper, or the like) of the sheet P, the thickness of the sheet P, the stiffness of the sheet P, and the like. It is not necessary that all of these pieces of sheet information can be set by the image forming apparatus, and only some pieces of sheet information may be set by the image forming apparatus. Further, the sheet information may be set by operating the external computer 200 via the external I/F 201.
The stacker control unit 210 is mounted on the stacker 100 (see FIG. 3 ) described in detail below. The stacker control unit 210 exchanges information with the CPU circuit unit 206 of the image forming apparatus 901 to control the entire stacker 100. That is, the stacker control unit 210 controls a belt drive motor 310 that drives a draw-in belt 16 described below and a belt lifting motor 311 serving as a third driving unit that lifts and lowers the draw-in belt 16. In addition, the stacker control unit 210 controls a lever lifting motor 312 serving as a first driving unit that lifts and lowers an urging lever 17 a and a tray lifting motor 313 serving as a second driving unit that lifts and lowers a stacking tray 6. Further, the stacker control unit 210 is connected to receive a signal from an upper surface position sensor 20 serving as a detection unit that detects the position of an upper surface of a sheet bundle stacked on the stacking tray 6. Details of the control of the stacker 100 will be described below.
The stacker control unit 210 is an example of a control unit that controls an operation of the stacker 100. A control function of the stacker control unit 210 in the present embodiment may be provided in a control unit outside the stacker 100. For example, the above-described control function may be incorporated in the CPU circuit unit 206 of the image forming apparatus 901, and the CPU circuit unit 206 may control the belt drive motor 310 and the like of the stacker 100 in the image forming apparatus 901.

Stacker

The stacker 100 which is the sheet stacking apparatus in the present embodiment will be described with reference to FIGS. 3 and 4A. FIG. 3 is a schematic view of a configuration of the stacker 100 according to the first embodiment. FIG. 4A is an enlarged view of a part of the stacker 100 (the periphery of the draw-in belt 16) in a state where the draw-in belt according to the first embodiment is lowered. In the description of the present embodiment, in a case where it is not necessary to distinguish between a sheet P1 having a high stiffness such as thick paper and a sheet P2 having a low stiffness such as plain paper and thin paper, the sheet P1 and the sheet P2 are simply referred to as “sheet P”.
The stacker 100 includes an inlet roller pair 1, a first switching member 2, a second switching member 21, a conveyance path 3, an outlet roller pair 4, and a sample tray 9. The stacker 100 further includes a discharge roller pair 5 serving as a conveyance unit, the stacking tray 6 serving as a stacking unit, grippers 7 a and 7 b, a gripper belt 8 serving as a transfer rotary member, a leading edge stopper 14, the draw-in belt 16 serving as an alignment rotary member, and side end regulating members 18. The leading edge stopper 14 has an abutment slope 14 a serving as an abutment surface and a leading edge abutment surface 14 b serving as an abutment portion.
The stacking tray 6 is an example of the stacking unit on which the sheet P discharged (conveyed) by the discharge roller pair 5 is stacked. The stacking tray 6 is lowered as the amount of sheets stacked on the stacking tray 6 increases. The discharge roller pair 5 is an example of the conveyance unit that conveys the sheet P toward the stacking unit. The leading edge abutment surface 14 b of the leading edge stopper 14 is an example of the abutment portion on which the leading edge of the sheet P in a sheet conveyance direction 13 (a downstream end of the sheet Pin the sheet conveyance direction 13) abuts. The draw-in belt 16 is an example of the alignment rotary member that moves the sheet P in the sheet conveyance direction 13 toward the abutment portion.
The inlet roller pair 1 receives and conveys the sheet P discharged from the image forming apparatus 901. The first switching member 2 switches a conveyance path of the sheet P fed from the inlet roller pair 1 between a conveyance path toward the outlet roller pair 4 or the sample tray 9 and a conveyance path (stacking path) toward the stacking tray 6. The second switching member 21 switches the conveyance path of the sheet P between the conveyance path 3 toward the outlet roller pair 4 and a conveyance path toward the sample tray 9. The outlet roller pair 4 discharges the sheet P conveyed through the conveyance path 3 to the outside of the stacker 100.
The discharge roller pair 5 conveys the sheet P in the sheet conveyance direction 13 and discharges the sheet P toward the stacking tray 6. The gripper belt 8 (timing belt) serving as the transfer rotary member is disposed above the stacking tray 6 and stretched around a driving pulley 11 and a driven pulley 12. The gripper belt 8 is rotationally driven in a rotation direction along the sheet conveyance direction 13 by rotation of the driving pulley 11 driven by a belt motor. The grippers 7 a and 7 b serving as gripping unit are attached to predetermined positions in a circumferential direction of the gripper belt 8, and rotate together with the gripper belt 8. The grippers 7 a and 7 b are configured to move (transfer) in the sheet conveyance direction 13 in a state where the grippers 7 a and 7 b grip (nip) the leading edge of the sheet P discharged from the discharge roller pair 5.
The stacking tray 6 is configured to be lifted and lowered inside the stacker 100. In the first embodiment, the stacking tray 6 is controlled to be lifted and lowered according to a sheet stacking amount based on a detection result of the sheet upper surface sensor that detects the sheet P at a predetermined height above the stacking tray 6 such that the upper surface of the sheet P stacked on the stacking tray 6 is maintained at a substantially constant height.
The leading edge stopper 14 is disposed at a downstream end portion of a stacking space on the stacking tray 6 in the sheet conveyance direction 13. The abutment slope 14 a of the leading edge stopper 14 protrudes downward from a lower surface of the gripper belt 8, and the leading edge abutment surface 14 b protrudes further downward than the abutment slope 14 a.
The abutment slope 14 a is an example of the abutment surface that abuts on the leading edge of the sheet P gripped by the gripper 7 a or 7 b to separate the sheet P from the gripper 7 a or 7 b. The abutment slope 14 a according to the present embodiment is an inclined surface inclined downward toward downstream in the sheet conveyance direction 13. The leading edge abutment surface 14 b is a surface that expands in a substantially vertical direction when viewed in a sheet width direction orthogonal to the sheet conveyance direction 13 (when viewed from the viewpoint of FIG. 3 ). The leading edge abutment surface 14 b serves as an alignment reference for the sheets P stacked on the stacking tray 6 in the sheet conveyance direction 13.
The draw-in belt 16 is disposed above the stacking tray 6 and is disposed downstream of an upstream end of the abutment slope 14 a and upstream of the leading edge abutment surface 14 b in the sheet conveyance direction 13. As illustrated in FIGS. 5A and 5B, a region where the draw-in belt 16 is in contact with the upper surface of the sheet P stacked on the stacking tray 6 and a region where an urging mechanism 17 is in contact with the sheet P overlap each other in the sheet conveyance direction 13. As illustrated in FIG. 4A, the draw-in belt 16 is sandwiched between a belt driving roller pair 15. The belt driving roller pair 15 is rotationally driven by a belt drive motor 310 (FIG. 2 ). By the rotation of the belt driving roller pair 15, the draw-in belt 16 is rotationally driven in a clockwise direction in the drawing (a rotation direction in which a lower portion of the draw-in belt 16 moves from upstream toward downstream in the sheet conveyance direction 13). An inner circumferential surface of the draw-in belt 16 is guided by guide rollers 151 at positions different from the belt driving roller pair 15.
The draw-in belt 16 is formed of an elastic material such as silicone rubber, ethylene propylene rubber (EPDM), or urethane rubber and has an endless shape. The draw-in belt 16 is disposed so as to be in contact with the upper surface of the sheet P stacked on the stacking tray 6 and elastically deformed. Due to the elasticity of the draw-in belt 16, a contact pressure when an outer peripheral surface of the draw-in belt 16 comes into contact with an upper surface of a sheet bundle on the stacking tray 6 becomes an appropriate magnitude. That is, the draw-in belt 16 is in contact with an upper surface of a sheet bundle stacked on the stacking tray 6 with a predetermined pressing force.
The draw-in belt 16 is also called an alignment belt that aligns the sheets P. The draw-in belt 16 may be a knurled belt subjected to knurling (embossing) in order to adjust a frictional force with respect to the sheet P.
As illustrated in FIG. 2 , the stacker 100 includes the upper surface position sensor 20 that detects the upper surface of the sheet P (sheet bundle). The stacker control unit 210 detects that the position of the upper surface of the sheet P stacked on the stacking tray 6 has reached a preset set position based on a detection signal from the upper surface position sensor 20.
As illustrated in FIG. 3 , the side end regulating members 18 are regulating members that regulate the position of the sheet P stacked on the stacking tray 6 in the sheet width direction. The side end regulating members 18 according to the present embodiment are a pair of regulating members movable in the sheet width direction between a regulating position where a side end position of the sheet P is regulated and a retracted position (sheet receiving position) where the side end regulating members 18 are retracted outward from the regulating position in the sheet width direction. The regulating position corresponds to a length (sheet width) of the sheet P in the sheet width direction.

Basic Operation of Stacker

A basic operation of the stacker 100 will be described with reference to FIG. 3 . When the sheet P is discharged from the image forming apparatus 901, the inlet roller pair 1 receives the sheet P. The sheet P is guided by the first switching member 2 and the second switching member 21 to a predetermined conveyance path according to a job setting set in advance by the operation unit 209 or the like. In a case where an apparatus (the sheet processing apparatus or the like) connected downstream of the stacker 100 is designated as a stacking location of the sheet P in the job setting, the sheet P passes through the conveyance path 3 and is discharged by the outlet roller pair 4. In a case where the sample tray 9 is designated as the stacking location of the sheets P in the job setting, the sheet P is discharged to the sample tray 9.
In a case where the stacking tray 6 is designated as the stacking location of the sheets P in the job setting, the stacker 100 performs the following sheet stacking operation (stacking processing). First, the sheet P fed from the inlet roller pair 1 is guided to the discharge roller pair 5 by the first switching member 2. The rotation of the gripper belt 8 is controlled to be synchronized with a timing at which the sheet P is fed from the discharge roller pair 5, and the leading edge of the sheet P fed from the discharge roller pair 5 is gripped by one of the two grippers 7 a and 7 b. Hereinafter, a case where the sheet P is gripped by the gripper 7 a will be described.
The sheet P is conveyed in the sheet conveyance direction 13 above the stacking tray 6 while being held by the discharge roller pair 5 and the gripper 7 a. When a leading edge Pa of the sheet P abuts on the abutment slope 14 a of the leading edge stopper 14, the leading edge Pa of the sheet P is released from the gripper 7 a and moves along the abutment slope 14 a toward the draw-in belt 16.
Here, a distance from a nip position of the discharge roller pair 5 in the sheet conveyance direction 13 to a contact position of the draw-in belt 16 is shorter than a sheet length of the sheet P stacked on the stacking tray 6. The contact position is a center position of a contact region between the draw-in belt 16 and the sheet P. The leading edge stopper 14 and the draw-in belt 16 are moved in advance to positions corresponding to the length of the sheet P stacked on the stacking tray 6 in the sheet conveyance direction 13 (hereinafter, simply referred to as the sheet length) based on the job setting. A position (stacking position) of the stacking tray 6 when the sheet P is discharged to the stacking tray 6 is controlled by the tray lifting motor 313 based on the position of the upper surface of the sheet bundle detected by the upper surface position sensor 20 (see FIG. 2 ). That is, the stacker control unit 210 lowers the stacking tray 6 by the amount of the stacked sheets P based on a detection result of the upper surface position sensor 20, thereby controlling a height at which the draw-in belt 16 comes into contact with the upper surface of the sheet bundle on the stacking tray 6. That is, the stacker control unit 210 controls the tray lifting motor 313 based on a detection result of the upper surface position sensor 20 such that the stacking unit is lowered as the amount of sheets stacked on the stacking tray 6 increases.
Therefore, after the leading edge Pa of the sheet P is released from the gripper 7 a, a leading edge portion of the sheet P comes into contact with the draw-in belt 16 before a trailing edge of the sheet P is released from the discharge roller pair 5, and receives a force (conveying force) in the sheet conveyance direction 13 from the draw-in belt 16. When the sheet P is moved in the sheet conveyance direction 13 by the draw-in belt 16, the leading edge Pa of the sheet P abuts on the leading edge abutment surface 14 b of the leading edge stopper 14. As a result, the position of the sheet P is aligned in the sheet conveyance direction 13. When the sheet P is skewed, skew correction is performed such that the leading edge Pa follows the leading edge abutment surface 14 b. Before the leading edge Pa of the sheet P abuts on the leading edge stopper 14, the trailing edge of the sheet P is released from the discharge roller pair 5.
When the image forming system 900 executes a job (continuous job) of continuously forming images on a plurality of sheets P and stacking the sheets P on the stacker 100, the above-described operation is repeatedly performed. When the user takes out the sheets P from the stacker 100, the user operates the operation unit 209 (or an open/close button provided on the stacker 100) to open the stacker 100 such that the user can access the stacking tray 6. In this case, the stacker control unit 210 (FIG. 2 ) having received the user operation lowers the stacking tray 6 from the stacking position to a lower position where the sheets P can be taken out.
The side end regulating members 18 are driven to move to the retracted position before the sheet P is discharged to the stacking tray 6, and move to the regulating position after the leading edge Pa of the sheet P is abutted on the leading edge abutment surface 14 b of the leading edge stopper 14 by the draw-in belt 16. Accordingly, alignment of the sheet bundle stacked on the stacking tray 6 in the sheet conveyance direction 13 and the sheet width direction is maintained.

Operation of Lifting and Lowering Draw-In Belt

Next, an operation of lifting and lowering the draw-in belt 16 will be described with reference to FIGS. 4A and 4B. FIGS. 4A and 4B are enlarged views of a part of the stacker according to the first embodiment, in which FIG. 4A illustrates a state in which the draw-in belt is lowered, and FIG. 4B illustrates a state in which the draw-in belt is lifted.
As illustrated in FIGS. 4A and 4B, the belt driving roller pair 15 is attached so as to be able to be lifted and lowered (relatively movable) with respect to the leading edge stopper 14, that is, the draw-in belt 16 is configured so as to be able to be lifted and lowered with respect to the leading edge stopper 14. Specifically, the belt lifting motor 311 lifts and lowers the belt driving roller pair 15 to vertically expand and contract the entire draw-in belt 16 rotated by the belt drive motor 310. As a result, a pressing force (pressure) of a portion where the draw-in belt 16 and the sheet P are in contact with each other changes. The draw-in belt 16 transmits the conveying force by being pressed against the sheet P. As a result, the sheet P abuts on the leading edge abutment surface 14 b, so that the sheets P stacked on the stacking tray 6 are aligned.
A driving amount of the belt lifting motor 311 for changing the pressing force of the draw-in belt 16 for the sheet P is determined by sheet information set by the user. The conveying force required for the draw-in belt 16 to convey the sheet P is assumed to be a reaction force of a frictional force generated between the sheet P and the draw-in belt 16. The pressing force to be applied from the draw-in belt 16 to the sheet P can be calculated from a weight of the sheet P that can be calculated from the longitudinal and lateral sizes (mm) and the grammage (gsm) of the sheet P and a friction coefficient of the draw-in belt 16. Then, a rotation amount of the belt drive motor 310 can be determined from the pressing force of the draw-in belt 16.
In the CPU circuit unit 206, pressing forces and rotation amounts corresponding to various types of sheet information are set in advance, and the belt drive motor 310 and the belt lifting motor 311 are driven so as to obtain an appropriate conveying force based on stacked sheet information. For example, in a case where a sheet on which the stacking operation is performed is thick paper or the like, since the grammage and the weight are larger than those of plain paper and thin paper, the draw-in belt 16 is lowered as illustrated in FIG. 4A. As a result, the pressing force and the rotation amount of the draw-in belt 16 are increased to increase the conveying force. Therefore, even in the case of the sheet P1 such as thick paper, it is possible to prevent a situation where the conveying force is insufficient, the sheet P1 stops midway, and the leading edge Pa of the sheet P1 does not abut on (reach) the leading edge abutment surface 14 b. On the other hand, for example, in a case where a sheet on which the stacking operation is performed is plain paper, thin paper, or the like, the grammage and the weight are smaller than those of thick paper, and thus, the draw-in belt 16 is lifted as illustrated in FIG. 4B. As a result, the pressing force and the rotation amount of the draw-in belt 16 are reduced to reduce the conveying force. Therefore, even in the case of the sheet P2 such as plain paper or thin paper, it is possible to prevent the leading edge Pa of the sheet P2 from being excessively pressed against the leading edge abutment surface 14 b and buckling.

Configuration of Urging Mechanism

Next, a configuration of the urging mechanism 17 according to the first embodiment will be described with reference to FIGS. 5A and 5B. FIG. 5A is an enlarged view of a part of the stacker in a state where the urging lever according to the first embodiment is lowered. FIG. 5B is an enlarged view of the part of the stacker in a state where the urging lever according to the first embodiment is lifted.
As illustrated in FIGS. 5A and 5B, the urging mechanism 17 included in the stacker 100 includes the urging lever 17 a serving as a first member, an urging plate 17 b serving as a second member, and an urging spring 17 c serving as an urging member. The urging lever 17 a is supported so as to be able to be lifted and lowered (relatively movable) with respect to the leading edge stopper 14, and can be driven to be lifted and lowered by a lever lifting motor 312. The urging plate 17 b is disposed to face the urging lever 17 a, and is in contact with a leading edge portion Pp of the sheet P from above. The urging spring 17 c is disposed to be contracted between the urging lever 17 a and the urging plate 17 b. That is, the urging plate 17 b is constantly urged toward the stacking tray 6 by an urging force of the urging spring 17 c, and is configured to press the leading edge portion Pp of the sheet P. Here, the leading edge portion Pp of the sheet is a portion having a predetermined distance (length) in the sheet conveyance direction from the leading edge Pa of the sheet, and particularly refers to a portion where curling or the like is likely to occur.
When the lever lifting motor 312 operates, the urging lever 17 a is lifted and lowered via a link mechanism (not illustrated) or the like, and a positional relationship with the upper surface of the sheet bundle changes. As a result, a compression amount of the urging spring 17 c changes, and an urging force F applied to the sheet P by the urging lever 17 a changes. For example, as illustrated in FIG. 5A, when the urging lever 17 a is lowered by the lever lifting motor 312, the urging spring 17 c is compressed such that a spring length of the urging spring 17 c becomes short, and the urging force F is increased as the compression amount is increased. On the other hand, for example, as illustrated in FIG. 5B, when the urging lever 17 a is lifted by the lever lifting motor 312, the urging spring 17 c is extended such that the spring length of the urging spring 17 c becomes long, and the urging force F is reduced as the compression amount is reduced.
In the CPU circuit unit 206, the urging forces F corresponding to various types of sheet information are set in advance, and the lever lifting motor 312 is controlled such that the urging mechanism 17 applies an appropriate urging force F based on the sheet information of the sheet P to be stacked, particularly, the thickness, grammage, stiffness, and the like of the sheet. The appropriate urging force F mentioned here is, for example, an urging force that can reliably suppress rising of the leading edge portion Pp even if the leading edge portion Pp of the sheet P is curled, and can enable the leading edge portion Pp to abut on the leading edge abutment surface 14 b without buckling the leading edge portion Pp of the sheet P. The urging force F applied to the sheet P may be calculated from the stiffness of various sheets or may be obtained by an experiment.
For example, in a case where a sheet on which the stacking operation is performed is thick paper or the like, the thickness and the grammage are larger and the stiffness is higher than those of plain paper or thin paper. Therefore, as illustrated in FIG. 5A, the urging lever 17 a is in a lowered state. Therefore, even in the case of the sheet P1 such as thick paper having a high stiffness, the sheet P1 can be pressed by the urging mechanism 17 so as to suppress curling and prevent the leading edge portion Pp from rising, and the leading edge Pa of the sheet P1 accurately abuts on the leading edge abutment surface 14 b. Therefore, the alignment of the sheets P1 can be improved.
On the other hand, for example, in a case where a sheet on which the stacking operation is performed is plain paper, thin paper, or the like, the thickness and the grammage are smaller and the stiffness is lower than those of the thick paper. Therefore, as illustrated in FIG. 5B, the urging lever 17 a is lifted higher than that for thick paper. Therefore, even in the case of the sheet P2 such as plain paper or thin paper having a low stiffness, the pressing force of the urging plate 17 b is not too strong and buckling does not occur in the middle, and the sheet P2 can be pressed by the urging mechanism 17 so as to suppress curling and prevent the leading edge portion Pp from raising. As a result, the leading edge Pa of the sheet P2 comes into contact with the leading edge abutment surface 14 b with high accuracy, and the alignment of the sheets P2 can be improved.

Control of Image Forming System in First Embodiment

Next, control of the image forming system 900 according to the first embodiment will be described with reference to FIG. 6 . FIG. 6 is a flowchart illustrating control of the image forming system 900 according to the first embodiment.
For example, when a power supply button (not illustrated) is operated in the operation unit 209 by the user and an ON signal from the power supply button is input to the CPU circuit unit 206, the CPU circuit unit 206 turns on the image forming apparatus 901 and the stacker 100 (S11). Then, the CPU circuit unit 206 operates the lever lifting motor 312 to move the urging lever 17 a to an initial position (S12). The initial position of the urging lever 17 a in the first embodiment is set to a position where the urging lever 17 a is farthest from the upper surface of the sheet bundle and the urging force F is smallest.
Here, for example, the type of the sheet is selected by the user via the operation unit 209 or an external computer, and the sheet information (any of the grammage, stiffness, thickness, and the like of the sheet) is set (S13). Then, the CPU circuit unit 206 acquires the sheet information by recording and storing the sheet information in the RAM 208 or the like. Then, the CPU circuit unit 206 instructs the stacker control unit 210 to lift or lower (here, lower) the urging lever 17 a by operating the lever lifting motor 312 based on the acquired sheet information (S14).
That is, it is assumed that a content of the sheet information is a sheet such as thick paper whose grammage is larger (second grammage), stiffness is higher (second stiffness), or thickness is larger (second thickness) than that of plain paper, thick paper, or the like. In this case, the stacker control unit 210 greatly lowers the urging lever 17 a from the initial position such that the urging force F of the urging mechanism 17 for urging the leading edge portion Pp of the sheet becomes a large urging force (a second urging force larger than a first urging force).
On the other hand, it is assumed that the content of the sheet information is a sheet such as plain paper or thin paper whose grammage is smaller (first grammage), stiffness is lower (first stiffness), or thickness is smaller (first thickness) that those of thick paper or the like. In this case, the stacker control unit 210 greatly lowers the urging lever 17 a from the initial position such that the urging force F of the urging mechanism 17 for urging the leading edge portion Pp of the sheet becomes a small urging force (the first urging force). In short, the stacker control unit 210 moves the position of the urging lever 17 a such that the urging force F of the urging mechanism 17 that presses the leading edge portion Pp of the sheet has an appropriate magnitude according to the type of the sheet.
Thereafter, when the user performs a print job start operation, the CPU circuit unit 206 operates the image forming apparatus 901 and the stacker 100, and performs the image forming operation and the sheet stacking operation (S15). Then, when the image forming operation and the sheet stacking operation for a set number of sheets by the user are completed, the print job is terminated (S16). When the print job is terminated and all the sheets P are stacked on the stacking tray 6, the CPU circuit unit 206 operates the lever lifting motor 312 to move the urging lever 17 a to the initial position (S17). In this way, the control of the stacker 100 according to the first embodiment ends.
As described above, in the image forming system 900 according to the first embodiment, the CPU circuit unit 206 adjusts the urging force F of the urging mechanism 17 according to the sheet information. As a result, it is possible to press the leading edge portions Pp of the sheets having different stiffness such as thick paper and thin paper with an appropriate urging force F. As a result, even a sheet having a high stiffness (large grammage or thickness) such as thick paper can be prevented from rising, and the leading edge of the sheet can accurately abut against the leading edge abutment surface 14 b. In addition, even a sheet having a low stiffness (small grammage or thickness) such as thin paper can be accurately abutted on the leading edge abutment surface 14 b without buckling of the leading edge portion Pp. Therefore, it is possible to improve the alignment of stacked sheets even for sheets having different stiffness such as thick paper and thin paper while meeting the needs for diversification of sheets. Modified Example of First Embodiment
Next, a modified example of the first embodiment will be described. In the first embodiment described above, the urging lever 17 a is driven to be lifted and lowered by the lever lifting motor 312. In the present modified example, the urging lever 17 a is attached to and fixedly supported by the draw-in belt 16, specifically, the belt driving roller pair 15. Thus, the urging lever 17 a is also lifted and lowered together by the belt lifting motor 311 that lifts and lowers the draw-in belt 16 (the belt driving roller pair 15). Alternatively, the draw-in belt 16 (the belt driving roller pair 15) is also lifted and lowered together by the lever lifting motor 312 that lifts and lowers the urging lever 17 a. The draw-in belt 16 is elastically deformed by coming into contact with the upper surface of the sheet stacked on the stacking tray 6, and an elastic deformation amount of the draw-in belt 16 changes as the belt driving roller pair 15 is lifted and lowered. In the present modified example, the belt driving roller pair 15 and the urging lever 17 a are lifted and lowered according to the sheet information. That is, the elastic deformation amount of the draw-in belt 16 is adjusted according to the sheet information. In addition, the stacker control unit 210 adjusts the position of the urging lever 17 a by the belt lifting motor 311 or the lever lifting motor 312 to adjust the urging force of the urging mechanism 17 and adjust the elastic deformation amount of the draw-in belt 16. Therefore, it is not necessary to provide the lever lifting motor 312 or the belt lifting motor 311, and cost reduction and miniaturization can be achieved, and the urging force F of the urging mechanism 17 can also be adjusted by being set according to the sheet information.

Second Embodiment

Next, a second embodiment partially modified from the first embodiment will be described with reference to the drawings. In the description of the second embodiment, the same reference numerals are used for the same parts as those of the first embodiment, and a description thereof will be omitted.

Configuration Example of Detection of Upper Surface Position

First, an example of a configuration and an operation of detecting a position of an upper surface of a sheet bundle stacked on a stacking tray 6 will be described with reference to FIGS. 8A and 8B. FIG. 8A is an enlarged view of a part of a stacker in a state where an upper surface position sensor according to the second embodiment does not detect a position detection lever pressed against the upper surface of the sheet bundle. FIG. 8B is an enlarged view of a part of the stacker in a state where the upper surface position sensor according to the second embodiment detects the position detection lever pressed against the upper surface of the sheet bundle.
As illustrated in FIGS. 8A and 8B, a stacker 100 includes a position detection lever 19 disposed pivotably with respect to a leading edge stopper 14, and an upper surface position sensor 20 that performs detection by a posture (rotation position) of the position detection lever 19. Specifically, the position detection lever 19 includes a pivot fulcrum 19 a pivotably supported by a support shaft or the like (not illustrated), a contact portion 19 b that is in contact with the upper surface of the sheet bundle, and a detection target portion 19 c detected by the upper surface position sensor 20. That is, the position detection lever 19 is pivotable about the pivot fulcrum 19 a as a fulcrum, and the contact portion 19 b is in contact with a stacking surface of the stacking tray 6 or the upper surface of the sheet bundle.
The position detection lever 19 changes the posture according to the position of the upper surface of the sheet bundle with respect to the pivot fulcrum 19 a. As illustrated in FIG. 8A, the position detection lever 19 is in contact with the upper surface of the sheet bundle (sheet P). However, a distance between the position of the upper surface of the sheet bundle and the pivot fulcrum 19 a is larger than a set distance, that is, the position of the upper surface of the sheet bundle is lower than a set position. Therefore, the detection target portion 19 c is not detected by the upper surface position sensor 20.
Thereafter, as illustrated in FIG. 8B, when the sheets P are sequentially stacked on the stacking tray 6 and the sheets P are stacked until the position of the upper surface of the sheet bundle reaches the set position, the contact portion 19 b that is in contact with the upper surface of the sheet bundle is lifted by the height of the upper surface of the sheet bundle. Therefore, the position detection lever 19 pivots about the pivot fulcrum 19 a as the fulcrum, and the detection target portion 19 c is detected by the upper surface position sensor 20. Therefore, the upper surface position sensor 20 detects that the position of the upper surface of the sheet bundle has been lifted to the set position. When the sheet P is further stacked on the upper surface of the sheet bundle and the position of the upper surface of the sheet bundle becomes higher than the set position, the detection target portion 19 c is not detected by the upper surface position sensor 20. Therefore, it is possible to detect that the position of the upper surface of the sheet bundle is higher than the set position based on a detection result of the upper surface position sensor 20 as a stacking operation for the sheets P is performed.
The height of the upper surface of the sheet bundle to be detected using the position detection lever 19 and the upper surface position sensor 20 can be arbitrarily set by changing the position of the pivot fulcrum 19 a, the shape of the detection target portion 19 c, a length between the pivot fulcrum 19 a and the contact portion 19 b, and the like. Alternatively, it is conceivable that the position detection lever 19 is configured to enter the upper surface position sensor 20 and the amount of entry is measured as another detection method using the position detection lever 19 and the upper surface position sensor 20. Furthermore, the present technology is not limited thereto, and any device that detects the position of the upper surface of the sheet bundle, such as a laser measurement sensor that measures an optical path length, may be used.

Change in Urging Force of Urging Mechanism by Lifting and Lowering of Stacking Tray

Subsequently, an operation of lifting and lowering the stacking tray 6 according to the second embodiment will be described with reference to FIGS. 7A, 7B, 7C, and 7D. FIG. 7A is an enlarged view of a part of the stacker in a state where the stacking tray according to the second embodiment is lifted. FIG. 7B is an enlarged view of a part of the stacker in a state where the stacking tray according to the second embodiment is lowered. FIG. 7C is an enlarged view of a part of the stacker in a state where sheets according to the second embodiment are stacked on the stacking tray and a sheet holding plate is lifted. FIG. 7D is an enlarged view of a part of the stacker in a state where the stacking tray is lowered after the sheets according to the second embodiment are stacked on the stacking tray.
In the first embodiment described above, the urging force F of the urging mechanism 17 is adjusted by lifting and lowering the urging lever 17 a. However, in the second embodiment, an urging force F of the urging mechanism 17 is adjusted by controlling lifting and lowering of the stacking tray 6 by a tray lifting motor 313.
That is, in the second embodiment, the urging lever 17 a is fixed to the leading edge stopper 14, and a positional relationship between the urging lever 17 a and the upper surface of the sheet bundle is adjusted by operating the tray lifting motor 313 to lift and lower the stacking tray 6. As a result, a compression amount of the urging spring 17 c changes, and the urging force F applied to a leading edge portion Pp of the sheet P conveyed by the urging mechanism 17 changes.
For example, it is assumed that a CPU circuit unit 206 determines that the sheet P to be conveyed is thick paper or the like and has a high stiffness, a large grammage, or a large thickness (a second stiffness, a second grammage, or a second thickness) based on sheet information. In this case, as illustrated in FIG. 7A, a stacker control unit 210 controls lifting and lowering of the stacking tray 6 such that a distance between the urging lever 17 a and the stacking tray 6 becomes shorter (smaller) to increase the compression amount of the urging spring 17 c, thereby increasing the urging force F.
On the other hand, for example, it is assumed that the CPU circuit unit 206 determines that the sheet P to be conveyed is plain paper, thin paper, or the like, and has a low stiffness, a small grammage, or a small thickness (a first stiffness, a first grammage, or a first thickness) based on the sheet information. In this case, as illustrated in FIG. 7B, the stacker control unit 210 controls lifting and lowering of the stacking tray 6 such that the distance between the urging lever 17 a and the stacking tray 6 becomes longer (larger) to reduce the compression amount of the urging spring 17 c, thereby reducing the urging force F.
Then, as illustrated in FIG. 7C, it is assumed that the sheets Pare sequentially stacked, and the upper surface position sensor 20 detects that the upper surface of the sheet bundle is higher than the set position. Then, the CPU circuit unit 206 operates the tray lifting motor 313 and to lower the stacking tray 6 as illustrated in FIG. 7D by a lowering amount H set based on the sheet information. Here, the lowering amount H is a distance from the position of an urging plate 17 b to which the appropriate urging force F is applied to the position of the upper surface of the sheet bundle that is lifted by the total thickness of the stacked sheets P. The lowering amount H may be arbitrarily set. For example, the lowering amount H may be set to the same value as the thickness of one sheet P, or may be set to the same value as the thickness of a sheet bundle including a plurality of sheets P. That is, the stacking tray 6 may be lowered every time one sheet P is stacked on the stacking tray 6, or may be lowered every time a predetermined number of sheets P are stacked on the stacking tray 6.
A timing at which the position of the upper surface of the sheet bundle is detected by the upper surface position sensor 20 is desirably set to an appropriate timing based on the sheet information such that the urging force F increased by the upper surface of the sheet bundle being lifted by the stacking of the sheets does not exceed the appropriate urging force F. Further, the urging force F applied to the leading edge portion Pp of the sheet P may be calculated from the stiffness of the sheet P or the like, or may be obtained by an experiment. The lowering amount H of the stacking tray 6 may be calculated from an upper limit and a lower limit of the appropriate urging force F and the thickness of the sheet P, or may be obtained by an experiment. The CPU circuit unit 206 can perform drive control of the tray lifting motor 313 such that the appropriate urging force F is applied based on the sheet information by setting the urging force F and the lowering amount H corresponding to the sheet information in advance. In the present embodiment, the set position is constant regardless of the sheet information. That is, even if the sheet information such as the thickness, stiffness, and grammage of the conveyed sheet changes, a target position of the upper surface of the sheet bundle stacked on the stacking tray 6 that is lifted and lowered is constant.

Control of Image Forming System in Second Embodiment

Next, control of an image forming system 900 according to the second embodiment will be described with reference to FIG. 9 . FIG. 9 is a flowchart illustrating control of the image forming system 900 according to the second embodiment.
For example, when a power supply button (not illustrated) is operated in an operation unit 209 by the user and an ON signal from the power supply button is input to the CPU circuit unit 206, the CPU circuit unit 206 turns on an image forming apparatus 901 and the stacker 100 (S21). Then, the CPU circuit unit 206 operates the tray lifting motor 313 to move the stacking tray 6 to an initial position (S22). The initial position of the stacking tray 6 in the second embodiment is set to a position of the stacking tray 6 for stacking the first sheet P.
Here, for example, the type of the sheet is selected by the user via the operation unit 209 or an external computer, and the sheet information (any of the grammage, stiffness, thickness, and the like of the sheet) is set (S23). Then, the CPU circuit unit 206 acquires the sheet information by recording and storing the sheet information in the RAM 208 or the like. Here, the CPU circuit unit 206 sets a set position of the stacking tray 6 to apply the appropriate urging force F to the leading edge portion Pp of the sheet P to be stacked on the stacking tray 6 based on the acquired sheet information. In other words, the CPU circuit unit 206 changes the set position of the stacking tray 6 according to the sheet information.
Then, in a case where the set position based on the sheet information needs to be moved from the initial position, the CPU circuit unit 206 instructs the stacker control unit 210 to operate the tray lifting motor 313 to lift and lower the stacking tray 6 to the set position (S24). In other words, the stacker control unit 210 controls the tray lifting motor 313 such that the position of the upper surface of the sheet bundle stacked on the stacking tray 6 becomes the set position. Therefore, the stacking tray 6 is moved to a position where the urging mechanism 17 applies the appropriate urging force F to the sheet P.
Thereafter, when the user performs a print job start operation (S25), the CPU circuit unit 206 operates the image forming apparatus 901 and the stacker 100, and performs the image forming operation and the sheet stacking operation (S26). As a result, the sheet P conveyed by a draw-in belt 16 is stacked so as to be aligned on the stacking tray 6 or the upper surface of the sheet bundle.
Here, if it is not detected that the position of the upper surface of the sheet bundle has become higher than the set position set in step S23 by the sheet P stacked in step S26 based on the detection of the upper surface position sensor 20 (NO in S27), the processing directly proceeds to step S29. On the other hand, it is assumed that it is detected that the position of the upper surface of the sheet bundle has become higher than the set position by the sheet P stacked in step S26 based on the detection of the upper surface position sensor 20 (YES in S27). In this case, the CPU circuit unit 206 controls the stacking tray 6 to be lowered by the lowering amount H by driving the tray lifting motor 313, that is, performs control such that the position of the upper surface of the sheet bundle becomes the set position (S28).
Then, the CPU circuit unit 206 determines whether or not the print job has been terminated, that is, whether or not the image forming operation and the sheet stacking operation for a set number of sheets by the user have been completed (S29). When the print job has not been terminated (NO in S29), the processing returns to step S26, and the processings from step S26 to step S28 are repeated. When the CPU circuit unit 206 determines that the print job has been terminated (YES in S29), this control is terminated.
As described above, in the image forming system 900 according to the second embodiment, the CPU circuit unit 206 adjusts the urging force F of the urging mechanism 17 by lifting and lowering the stacking tray 6 according to the sheet information. As a result, it is possible to press the leading edge portions Pp of the sheets having different stiffness such as thick paper and thin paper with an appropriate urging force F. As a result, even a sheet having a high stiffness (large grammage or thickness) such as thick paper can be prevented from rising, and the leading edge of the sheet can accurately abut against the leading edge abutment surface 14 b. In addition, even a sheet having a low stiffness (small grammage or thickness) such as thin paper can be accurately abutted on the leading edge abutment surface 14 b without buckling of the leading edge portion Pp. Therefore, it is possible to improve the alignment of stacked sheets even for sheets having different stiffness such as thick paper and thin paper while meeting the needs for diversification of sheets.

Other Embodiments

In the first and second embodiments described above, a case where the stacker 100 includes the draw-in belt 16, and the leading edge of the sheet is drawn in to the leading edge abutment surface 14 b to be aligned has been described. However, the present technology is not limited thereto, and for example, the sheet may be conveyed by a conveyance roller pair positioned upstream in the sheet conveyance direction, and the leading edge of the sheet may be abutted on the leading edge abutment surface 14 b to be aligned. Therefore, the sheet stacking apparatus does not have to include the draw-in belt 16.
In the first and second embodiments, the draw-in belt 16 has been described as drawing in the leading edge of the sheet to the leading edge abutment surface 14 b by way of example. However, the present technology is not limited thereto, and for example, a paddle that rotates to draw in the leading edge of the sheet to the leading edge abutment surface 14 b may be used, that is, any alignment rotary member that moves and aligns the sheet may be used.
In the first and second embodiments, a case where the sheet is transferred above the sheet bundle using the gripper belt 8 and the grippers 7 a and 7 b to prevent deterioration in alignment caused by the conveyed sheet touching the sheet already stacked on the stacking tray 6 has been described. However, the present technology is not limited thereto, and a sheet transfer mechanism such as the gripper belt 8 or the grippers 7 a and 7 b does not have to be provided as long as the sheet stacking apparatus does not stack a sheet having a large length in the conveyance direction.
In the first and second embodiments, a configuration in which the urging mechanism 17 includes the urging lever 17 a, the urging plate 17 b, and the urging spring 17 c has been described an example. However, the present technology is not limited thereto, and the urging mechanism may have any structure. For example, the urging force may be adjusted by expanding and contracting a solenoid according to the sheet information, or the urging force may be adjusted by using a magnetic force.
In the first and second embodiments, a case where the urging force F of the urging mechanism 17 is adjusted according to any one of the thickness of the sheet, the stiffness of the sheet, and the grammage of the sheet as the sheet information has been described. However, the present technology is not limited thereto, and any sheet information may be used as long as the sheet information can suppress curling of the leading edge portion of the sheet by pressing, and the sheet information is used to perform adjustment such that the sheet is not buckled by the urging force of the urging mechanism. Any one piece of sheet information of the thickness of the sheet, the stiffness of the sheet, and the grammage of the sheet may be input to the CPU circuit unit 206 as the sheet information, and not all the pieces of sheet information are required. The sheet information can also be referred to as an attribute of the sheet.
The upper surface position sensor 20 and the position detection lever 19 described in the second embodiment are examples of means for detecting the position of the upper surface of the sheet bundle, and may be used in the first embodiment, or other sensors may be used in the first and second embodiments.
Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2023-084829, filed May 23, 2023, which is hereby incorporated by reference herein in its entirety.

Claims

What is claimed is:

1. A sheet stacking apparatus comprising:

a conveyance unit configured to convey a sheet;

a stacking unit on which the sheet conveyed by the conveyance unit is stacked, the stacking unit being configured to be lowered as an amount of the sheets stacked on the stacking unit increases;

an abutment portion on which a leading edge of the sheet conveyed by the conveyance unit abuts;

an urging unit configured to urge a leading edge portion, of the sheet, abutting on the abutment portion toward the stacking unit; and

a control unit configured to adjust an urging force of the urging unit according to sheet information of the sheet conveyed toward the abutment portion.

2. The sheet stacking apparatus according to claim 1, wherein the sheet information includes information regarding a thickness of the sheet, and

the control unit is configured to adjust the urging force of the urging unit to a first urging force in a case where the sheet conveyed toward the abutment portion has a first thickness, and to adjust the urging force of the urging unit to a second urging force larger than the first urging force in a case where the sheet conveyed toward the abutment portion has a second thickness larger than the first thickness.

3. The sheet stacking apparatus according to claim 1, wherein the sheet information includes information regarding a stiffness of the sheet, and

the control unit is configured to adjust the urging force of the urging unit to a first urging force in a case where the sheet conveyed toward the abutment portion has a first stiffness, and to adjust the urging force of the urging unit to a second urging force larger than the first urging force in a case where the sheet conveyed toward the abutment portion has a second stiffness higher than the first stiffness.

4. The sheet stacking apparatus according to claim 1, wherein the sheet information includes information regarding a grammage of the sheet, and

the control unit is configured to adjust the urging force of the urging unit to a first urging force in a case where the sheet conveyed toward the abutment portion has a first grammage, and to adjust the urging force of the urging unit to a second urging force larger than the first urging force in a case where the sheet conveyed toward the abutment portion has a second grammage larger than the first grammage.

5. The sheet stacking apparatus according to claim 1, wherein the urging unit includes a first member, a second member that is disposed to face the first member and contacts with the sheet, and an urging member disposed between the first member and the second member.

6. The sheet stacking apparatus according to claim 5, further comprising a first driving unit configured to lift and lower the first member,

wherein the control unit is configured to adjust the urging force of the urging unit by adjusting a position of the first member by the first driving unit.

7. The sheet stacking apparatus according to claim 6, further comprising:

a second driving unit configured to lift and lower the stacking unit; and

a detection unit configured to detect that a position of an upper surface of a sheet bundle stacked on the stacking unit is a set position,

wherein the control unit is configured to control the second driving unit such that the position of the upper surface of the sheet bundle stacked on the stacking unit becomes the set position.

8. The sheet stacking apparatus according to claim 7, wherein the set position is constant regardless of the sheet information.

9. The sheet stacking apparatus according to claim 6, further comprising an alignment rotary member configured to rotate while contacting with the sheet stacked on the stacking unit to move the sheet toward the abutment portion and align the sheet,

wherein the first driving unit is configured to lift and lower the alignment rotary member together with the first member.

10. The sheet stacking apparatus according to claim 6, further comprising:

an alignment rotary member configured to rotate while contacting with the sheet stacked on the stacking unit to move the sheet toward the abutment portion and align the sheet; and

a third driving unit configured to change a pressing force of the alignment rotary member with respect to the sheet stacked on the stacking unit.

11. The sheet stacking apparatus according to claim 1, further comprising:

a second driving unit configured to lift and lower the stacking unit; and

a detection unit configured to detect a position of an upper surface of a sheet bundle stacked on the stacking unit,

wherein the control unit is configured to control the second driving unit based on a detection result of the detection unit such that the stacking unit is lowered as the amount of the sheets stacked on the stacking unit increases.

12. The sheet stacking apparatus according to claim 1, further comprising an alignment rotary member configured to rotate while contacting with the sheet stacked on the stacking unit to move the sheet toward the abutment portion and align the sheet.

13. The sheet stacking apparatus according to claim 12, wherein the alignment rotary member is elastically deformed by coming into contact with an upper surface of the sheet stacked on the stacking unit, and

an elastic deformation amount of the alignment rotary member is adjusted according to the sheet information.

14. The sheet stacking apparatus according to claim 12, wherein a region where the alignment rotary member comes into contact with an upper surface of the sheet stacked on the stacking unit and a region where the urging unit comes into contact with the sheet overlap each other in a sheet conveyance direction.

15. The sheet stacking apparatus according to claim 12, wherein the urging unit includes a first member, a second member that is disposed to face the first member and contacts with the sheet, and an urging member disposed between the first member and the second member,

the sheet stacking apparatus further comprises:

a first driving unit configured to lift and lower the first member; and

a roller configured to support the alignment rotary member,

the alignment rotary member is elastically deformed by coming into contact with an upper surface of the sheet stacked on the stacking unit, and

the control unit is configured to adjust the urging force of the urging unit and adjust an elastic deformation amount of the alignment rotary member by adjusting a position of the first member by the first driving unit.

16. The sheet stacking apparatus according to claim 1, further comprising a second driving unit configured to lift and lower the stacking unit,

wherein the control unit is configured to adjust the urging force of the urging unit by adjusting a position of an upper surface of a sheet bundle stacked on the stacking unit by the second driving unit.

17. The sheet stacking apparatus according to claim 16, further comprising a detection unit configured to detect that the position of the upper surface of the sheet bundle stacked on the stacking unit is a set position,

wherein the control unit is configured to

(i) change the set position according to the sheet information and

(ii) control the second driving unit such that the position of the upper surface of the sheet bundle stacked on the stacking unit becomes the set position.

18. The sheet stacking apparatus according to claim 1, further comprising:

a transfer rotary member disposed above the stacking unit;

a gripping unit attached to the transfer rotary member and configured to transfer the sheet in a sheet conveyance direction in a state of gripping the leading edge of the sheet fed from the conveyance unit in the sheet conveyance direction; and

an abutment surface configured to come into contact with the leading edge of the sheet to separate the leading edge of the sheet from the gripping unit.

19. An image forming system comprising:

an image forming apparatus configured to form an image on a sheet; and

the sheet stacking apparatus according to claim 1, the sheet stacking apparatus being configured to stack the sheet on which the image is formed by the image forming apparatus.